New York, Dec. 14: The US government is beginning a project designed to unlock the genetic abnormalities that contribute to cancer, an effort that would exceed the Human Genome Project in complexity and could eventually lead to new diagnostic tests and treatments for the disease.

Government officials said they would spend $100 million over three years on a pilot phase of the project, which will be called The Cancer Genome Atlas. “This is a revolutionary project,” Anna D. Barker, deputy director of the National Cancer Institute, said at a news briefing in Washington. “It’s going to empower all cancer researchers with an entire new set of data to work with.” The cancer institute will contribute half of the money with the other half provided by the National Human Genome Research Institute. Both are part of the National Institutes of Health (NIH).

Scientists have long known that genetic mutations that accumulate in normal cells over a person’s lifetime can make those cells cancerous.

About 300 genes involved in cancer are already known, and there are a handful of drugs that work by interfering with specific genetic abnormalities.

The drug Gleevec, which blocks a particular genetic change that causes a type of leukaemia , produces remissions in most patients with that form of the disease. Some studies have shown that the lung cancer drug Iressa is likely to work very well for the 10 per cent of patients who have a particular type of mutation but barely at all for others. But federal officials and many cancer researchers say that a more systematic search could find many more genes and gene variations that play an important role in determining how aggressive a cancer will be and what drugs might work best. The first fruits, such as new diagnostic tests, may be seen in several years. “We are still working with an incomplete compass,” said Francis S. Collins, director of the National Human Genome Research Institute. “The time is right to bring the full power of genomics to bear on the problem of cancer.”

The project would involve determining the sequence of letters in the DNA of tumour cells obtained from biopsies or surgery. The initials of the project’s name, TCGA, represent the four letters of the genetic code.

Scientists will also look for other changes like duplications or deletions of genes, or differences between cells in which genes are turned on or off.

In February a committee advising the cancer institute proposed such a project, which it estimated, would cost $1.35 billion over nine years.

But government officials said they would first assess the results of the three-year pilot project before deciding whether a full programme would be worthwhile. They said it was too early to estimate how much a full project would cost.

The pilot phase will involve studying hundreds of tumour samples from two or three types of cancer, which have not been chosen yet. The decision will depend upon factors like the availability of tumour samples. A full project could involve studying 50 types of cancer.

Some scientists have expressed concern about the project, saying it may divert grant money from individual investigators at a time when the NIH budget is not growing rapidly, as it was a few years ago.

Some have also said that cancer cells are so genetically heterogeneous — two cells in the same tumour can differ in their mutations — that it will be hard to find mutations that are meaningful and could lead to new drugs. “We need to be able to look cancer patients and their families in the eye and say, ‘We are spending our money in the best way we know to find a cure for you’,” Stephen J. Elledge of Harvard and Gregory J. Hannon of Cold Spring Harbor Laboratory wrote in Science in October.

To minimise the risk of failure, the pilot project will choose types of cancer that have relatively little variability.